This happened about 5 miles away from my house. 

Investigators say Selvy was robbed of alcohol scuffled with a man identified as 36-year-old Bobby Baughman.

Police say Baughman struck Selvy in the head with a wrench and Selvy retaliated by retrieving a pistol from his vehicle and fatally shooting Baughman 

The key phrase? 

"retaliated by retrieving a pistol from his vehicle" 

Whoops: Mr. Selvy's life was not in danger at the point where he used deadly force. Therefore, he is facing second degree murder charges.

Bottom line is, a firearm is to be used only for direct and urgent threats to your life or the life of someone else. Getting attacked with lethal force, (and unless my years of playing "Clue!" were all wasted, a blow to the head with a wrench is considered lethal force), would be considered by most people (your jury may vary) to be reason enough to respond with lethal force. 

But getting conked on the noggin, walking to your car and THEN using lethal force isn't.